19.7 Troubleshooting and Repairing Keyboards

Good
keyboards are so cheap that spending much time troubleshooting or
repairing them is counterproductive. Membrane keyboards are
irreparable in practical terms. Mechanical and capacitive keyboards
can be repaired, but with parts expensive and difficult to find and
technicians charging $50+ per hour, it's cheaper
just to buy a new one. The same goes for repairing a keyboard
yourself, unless your time is worth nothing an hour.

If a keyboard stops working or behaves strangely, check to make sure
the cables are connected properly. If everything appears to be
correct, it's worth doing a simple swap to verify
whether the problem is the keyboard or the PC. If a known-good
keyboard also fails to work, the problem is most likely caused by a
defective keyboard interface on the motherboard, for which the only
realistic solutions are to substitute a USB keyboard or replace the
motherboard. If the known-good keyboard works, replace the defective
keyboard.